//#define _CRT_SECURE_NO_WARNINGS
//#include<stdio.h>
//#include<math.h>
//int main()
//{
//	double x1 = 0, y1 = 0, x2 = 0, y2 = 0;
//
//	while (scanf("%lf %lf %lf %lf", &x1, &y1, &x2, &y2)!=EOF)
//	{
//		printf("%.2lf\n", sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2)));
//	}
//
//	return 0;
//}